Recent reviews describe different alternatives, especially based on Mn and Fe compounds (Bieleman, J. H. in Additives in Plastics and Paints, Chimia, 56, 184 (2002); Bieleman, J. H., Marcomol. Symp., 187, 811 (2002); van Gorkum R, Bouwman E, Coord. Chem. Rev., 249, 1709 (2005)).
WO 03/093384 describes the use of transition-metal salts or complexes based on pyrazoles, aliphatic and aromatic amines, 2,2′-bipyridine, 1,10′-phenanthroline, 1,4,7-trimethyl-1,4,7-triazacyclononane in combination with a reducing agent as drying agent. Especially Fe and Mn salts and complexes were preferred in combination with ascorbic acid or derivatives thereof. WO03/093384 demonstrates that iron compounds have a rather poor activity and hence high dosages are needed to get satisfactory drying activity. A drawback of using iron compounds at high levels is that an unwanted yellowish/brownish colour is imparted to the mix.